Hey , yeah I have a small portable forge and I cast iron metal bender which I usually use to do it on. The metal bender is on a pedestal and bolted to the ground. Defo not an operation I can make mobile , only other way you could do it would be using my blacksmith vice and anvil , again really not something that can be mobile! As I said sometime I need to be able to weld slightly different shapes etc which simple bending can’t achieve.For simple brackets I'd always want to heat and bend, even with a decent weld (which will take longer) you are going to be introducing heat affected zones, grain changes and a whole lot of faff. You tend to find a lot of defects in stops and starts, brackets like the ones shown are effectively a stop start. Have you looked at portable induction heaters for heat source for bending or oxy acetylene for heating/welding? Don't want to discourage anyone from learning to MMA weld, great skill to learn and one that will serve you well for going onto other welding processes as well but given the types of examples shown not sure it is a great application for that process.